Do the authors have any comment or thoughts about the recent Microsoft announcement (or so it's been understood) that Linq to Entities, not Linq to Sql, is going forward to be the Linq way to access data stores. It looks like Linq to Sql is not going to receive much further work.

Personally, I don't really have much to add to what has already been said. You pretty much summed it up already in your message.
LINQ to SQL will not disappear, but it will not evolve as it's the Entity Framework (and so LINQ to Entities) that now receives Microsoft's involvement.

It's now up to you to decide which way you want to go.
You can decide to migrate your existing LINQ to SQL projects to Entity Framework, or maintain them as is. Either way can work.
As for new projects, you should probably favor Entity Framework. But LINQ to SQL is still a good choice for small and quick projects.

Really, given Microsoft's announcement, you can decide what you want. You are not forced to move to Entity Framework. LINQ to SQL is not dead. It just won't evolve much now.

Thank you. I hope you'll be able to release a book or update with info on Linq To Entities (and a comparison of L2S and L2E). I'll probably go with L2E for new projects, because it seems, from what I've read, that they expect the next release of L2E to have all the advantages they each separately have now.